360 lines
13 KiB
Perl
360 lines
13 KiB
Perl
package Time::HiRes;
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use strict;
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use vars qw($VERSION $XS_VERSION @ISA @EXPORT @EXPORT_OK $AUTOLOAD);
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require Exporter;
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require DynaLoader;
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@ISA = qw(Exporter DynaLoader);
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@EXPORT = qw( );
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@EXPORT_OK = qw (usleep sleep ualarm alarm gettimeofday time tv_interval
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getitimer setitimer
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ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF
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d_usleep d_ualarm d_gettimeofday d_getitimer d_setitimer
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d_nanosleep);
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$VERSION = '1.59';
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$XS_VERSION = $VERSION;
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$VERSION = eval $VERSION;
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sub AUTOLOAD {
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my $constname;
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($constname = $AUTOLOAD) =~ s/.*:://;
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die "&Time::HiRes::constant not defined" if $constname eq 'constant';
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my ($error, $val) = constant($constname);
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if ($error) { die $error; }
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{
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no strict 'refs';
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*$AUTOLOAD = sub { $val };
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}
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goto &$AUTOLOAD;
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}
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bootstrap Time::HiRes;
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# Preloaded methods go here.
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sub tv_interval {
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# probably could have been done in C
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my ($a, $b) = @_;
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$b = [gettimeofday()] unless defined($b);
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(${$b}[0] - ${$a}[0]) + ((${$b}[1] - ${$a}[1]) / 1_000_000);
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}
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# Autoload methods go after =cut, and are processed by the autosplit program.
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1;
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__END__
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=head1 NAME
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Time::HiRes - High resolution alarm, sleep, gettimeofday, interval timers
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=head1 SYNOPSIS
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use Time::HiRes qw( usleep ualarm gettimeofday tv_interval );
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usleep ($microseconds);
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ualarm ($microseconds);
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ualarm ($microseconds, $interval_microseconds);
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$t0 = [gettimeofday];
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($seconds, $microseconds) = gettimeofday;
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$elapsed = tv_interval ( $t0, [$seconds, $microseconds]);
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$elapsed = tv_interval ( $t0, [gettimeofday]);
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$elapsed = tv_interval ( $t0 );
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use Time::HiRes qw ( time alarm sleep );
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$now_fractions = time;
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sleep ($floating_seconds);
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alarm ($floating_seconds);
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alarm ($floating_seconds, $floating_interval);
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use Time::HiRes qw( setitimer getitimer
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ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF );
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setitimer ($which, $floating_seconds, $floating_interval );
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getitimer ($which);
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=head1 DESCRIPTION
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The C<Time::HiRes> module implements a Perl interface to the C<usleep>,
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C<ualarm>, C<gettimeofday>, and C<setitimer>/C<getitimer> system calls, in other
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words, high resolution time and timers. See the L</EXAMPLES> section below
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and the test scripts for usage; see your system documentation for the
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description of the underlying C<nanosleep> or C<usleep>, C<ualarm>,
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C<gettimeofday>, and C<setitimer>/C<getitimer> calls.
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If your system lacks C<gettimeofday()> or an emulation of it you don't
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get C<gettimeofday()> or the one-argument form of C<tv_interval()>. If your system lacks all of
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C<nanosleep()>, C<usleep()>, and C<select()>, you don't get
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C<Time::HiRes::usleep()> or C<Time::HiRes::sleep()>. If your system lacks both
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C<ualarm()> and C<setitimer()> you don't get
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C<Time::HiRes::ualarm()> or C<Time::HiRes::alarm()>.
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If you try to import an unimplemented function in the C<use> statement
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it will fail at compile time.
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If your subsecond sleeping is implemented with C<nanosleep()> instead of
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C<usleep()>, you can mix subsecond sleeping with signals since
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C<nanosleep()> does not use signals. This, however is unportable, and you
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should first check for the truth value of C<&Time::HiRes::d_nanosleep> to
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see whether you have nanosleep, and then carefully read your
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C<nanosleep()> C API documentation for any peculiarities. (There is no
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separate interface to call C<nanosleep()>; just use C<Time::HiRes::sleep()>
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or C<Time::HiRes::usleep()> with small enough values.)
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Unless using C<nanosleep> for mixing sleeping with signals, give
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some thought to whether Perl is the tool you should be using for work
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requiring nanosecond accuracies.
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The following functions can be imported from this module.
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No functions are exported by default.
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=over 4
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=item gettimeofday ()
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In array context returns a two-element array with the seconds and
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microseconds since the epoch. In scalar context returns floating
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seconds like C<Time::HiRes::time()> (see below).
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=item usleep ( $useconds )
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Sleeps for the number of microseconds specified. Returns the number
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of microseconds actually slept. Can sleep for more than one second,
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unlike the C<usleep> system call. See also C<Time::HiRes::sleep()> below.
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=item ualarm ( $useconds [, $interval_useconds ] )
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Issues a C<ualarm> call; the C<$interval_useconds> is optional and
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will be zero if unspecified, resulting in C<alarm>-like behaviour.
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=item tv_interval
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tv_interval ( $ref_to_gettimeofday [, $ref_to_later_gettimeofday] )
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Returns the floating seconds between the two times, which should have
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been returned by C<gettimeofday()>. If the second argument is omitted,
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then the current time is used.
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=item time ()
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Returns a floating seconds since the epoch. This function can be
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imported, resulting in a nice drop-in replacement for the C<time>
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provided with core Perl; see the L</EXAMPLES> below.
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B<NOTE 1>: This higher resolution timer can return values either less
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or more than the core C<time()>, depending on whether your platform
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rounds the higher resolution timer values up, down, or to the nearest second
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to get the core C<time()>, but naturally the difference should be never
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more than half a second.
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B<NOTE 2>: Since Sunday, September 9th, 2001 at 01:46:40 AM GMT, when
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the C<time()> seconds since epoch rolled over to 1_000_000_000, the
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default floating point format of Perl and the seconds since epoch have
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conspired to produce an apparent bug: if you print the value of
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C<Time::HiRes::time()> you seem to be getting only five decimals, not six
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as promised (microseconds). Not to worry, the microseconds are there
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(assuming your platform supports such granularity in first place).
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What is going on is that the default floating point format of Perl
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only outputs 15 digits. In this case that means ten digits before the
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decimal separator and five after. To see the microseconds you can use
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either C<printf>/C<sprintf> with C<"%.6f">, or the C<gettimeofday()> function in
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list context, which will give you the seconds and microseconds as two
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separate values.
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=item sleep ( $floating_seconds )
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Sleeps for the specified amount of seconds. Returns the number of
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seconds actually slept (a floating point value). This function can be
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imported, resulting in a nice drop-in replacement for the C<sleep>
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provided with perl, see the L</EXAMPLES> below.
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=item alarm ( $floating_seconds [, $interval_floating_seconds ] )
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The C<SIGALRM> signal is sent after the specified number of seconds.
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Implemented using C<ualarm()>. The C<$interval_floating_seconds> argument
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is optional and will be zero if unspecified, resulting in C<alarm()>-like
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behaviour. This function can be imported, resulting in a nice drop-in
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replacement for the C<alarm> provided with perl, see the L</EXAMPLES> below.
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B<NOTE 1>: With some operating system and Perl release combinations
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C<SIGALRM> restarts C<select()>, instead of interuping it.
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This means that an C<alarm()> followed by a C<select()>
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may together take the sum of the times specified for the the
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C<alarm()> and the C<select()>, not just the time of the C<alarm()>.
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=item setitimer ( $which, $floating_seconds [, $interval_floating_seconds ] )
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Start up an interval timer: after a certain time, a signal arrives,
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and more signals may keep arriving at certain intervals. To disable a
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timer, use C<$floating_seconds> of zero. If the C<$interval_floating_seconds>
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is set to zero (or unspecified), the timer is disabled B<after> the
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next delivered signal.
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Use of interval timers may interfere with C<alarm()>, C<sleep()>,
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and C<usleep()>. In standard-speak the "interaction is unspecified",
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which means that I<anything> may happen: it may work, it may not.
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In scalar context, the remaining time in the timer is returned.
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In list context, both the remaining time and the interval are returned.
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There are usually three or four interval timers available: the C<$which>
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can be C<ITIMER_REAL>, C<ITIMER_VIRTUAL>, C<ITIMER_PROF>, or C<ITIMER_REALPROF>.
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Note that which ones are available depends: true UNIX platforms usually
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have the first three, but (for example) Win32 and Cygwin have only
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C<ITIMER_REAL>, and only Solaris seems to have C<ITIMER_REALPROF> (which is
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used to profile multithreaded programs).
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C<ITIMER_REAL> results in C<alarm()>-like behavior. Time is counted in
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I<real time>; that is, wallclock time. C<SIGALRM> is delivered when
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the timer expires.
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C<ITIMER_VIRTUAL> counts time in (process) I<virtual time>; that is, only
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when the process is running. In multiprocessor/user/CPU systems this
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may be more or less than real or wallclock time. (This time is also
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known as the I<user time>.) C<SIGVTALRM> is delivered when the timer expires.
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C<ITIMER_PROF> counts time when either the process virtual time or when
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the operating system is running on behalf of the process (such as I/O).
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(This time is also known as the I<system time>.) (The sum of user
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time and system time is known as the I<CPU time>.) C<SIGPROF> is
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delivered when the timer expires. C<SIGPROF> can interrupt system calls.
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The semantics of interval timers for multithreaded programs are
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system-specific, and some systems may support additional interval
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timers. See your C<setitimer()> documentation.
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=item getitimer ( $which )
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Return the remaining time in the interval timer specified by C<$which>.
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In scalar context, the remaining time is returned.
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In list context, both the remaining time and the interval are returned.
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The interval is always what you put in using C<setitimer()>.
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=back
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=head1 EXAMPLES
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use Time::HiRes qw(usleep ualarm gettimeofday tv_interval);
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$microseconds = 750_000;
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usleep $microseconds;
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# signal alarm in 2.5s & every .1s thereafter
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ualarm 2_500_000, 100_000;
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# get seconds and microseconds since the epoch
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($s, $usec) = gettimeofday;
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# measure elapsed time
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# (could also do by subtracting 2 gettimeofday return values)
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$t0 = [gettimeofday];
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# do bunch of stuff here
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$t1 = [gettimeofday];
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# do more stuff here
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$t0_t1 = tv_interval $t0, $t1;
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$elapsed = tv_interval ($t0, [gettimeofday]);
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$elapsed = tv_interval ($t0); # equivalent code
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#
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# replacements for time, alarm and sleep that know about
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# floating seconds
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#
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use Time::HiRes;
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$now_fractions = Time::HiRes::time;
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Time::HiRes::sleep (2.5);
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Time::HiRes::alarm (10.6666666);
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use Time::HiRes qw ( time alarm sleep );
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$now_fractions = time;
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sleep (2.5);
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alarm (10.6666666);
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# Arm an interval timer to go off first at 10 seconds and
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# after that every 2.5 seconds, in process virtual time
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use Time::HiRes qw ( setitimer ITIMER_VIRTUAL time );
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$SIG{VTALRM} = sub { print time, "\n" };
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setitimer(ITIMER_VIRTUAL, 10, 2.5);
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=head1 C API
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In addition to the perl API described above, a C API is available for
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extension writers. The following C functions are available in the
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modglobal hash:
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name C prototype
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--------------- ----------------------
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Time::NVtime double (*)()
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Time::U2time void (*)(UV ret[2])
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Both functions return equivalent information (like C<gettimeofday>)
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but with different representations. The names C<NVtime> and C<U2time>
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were selected mainly because they are operating system independent.
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(C<gettimeofday> is Unix-centric, though some platforms like VMS have
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emulations for it.)
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Here is an example of using C<NVtime> from C:
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double (*myNVtime)();
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SV **svp = hv_fetch(PL_modglobal, "Time::NVtime", 12, 0);
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if (!svp) croak("Time::HiRes is required");
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if (!SvIOK(*svp)) croak("Time::NVtime isn't a function pointer");
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myNVtime = INT2PTR(double(*)(), SvIV(*svp));
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printf("The current time is: %f\n", (*myNVtime)());
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=head1 DIAGNOSTICS
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=head2 negative time not invented yet
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You tried to use a negative time argument.
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=head2 internal error: useconds < 0 (unsigned ... signed ...)
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Something went horribly wrong-- the number of microseconds that cannot
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become negative just became negative. Maybe your compiler is broken?
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=head1 CAVEATS
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Notice that the core C<time()> maybe rounding rather than truncating.
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What this means is that the core C<time()> may be reporting the time
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as one second later than C<gettimeofday()> and C<Time::HiRes::time()>.
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Adjusting the system clock (either manually or by services like ntp)
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may cause problems, especially for long running programs that assume
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a monotonously increasing time (note that all platforms do not adjust
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time as gracefully as UNIX ntp does). For example in Win32 (and derived
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platforms like Cygwin and MinGW) the Time::HiRes::time() may temporarily
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drift off from the system clock (and the original time()) by up to 0.5
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seconds. Time::HiRes will notice this eventually and recalibrate.
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=head1 AUTHORS
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D. Wegscheid <wegscd@whirlpool.com>
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R. Schertler <roderick@argon.org>
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J. Hietaniemi <jhi@iki.fi>
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G. Aas <gisle@aas.no>
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=head1 COPYRIGHT AND LICENSE
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Copyright (c) 1996-2002 Douglas E. Wegscheid. All rights reserved.
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Copyright (c) 2002,2003,2004 Jarkko Hietaniemi. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the same terms as Perl itself.
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=cut
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